Dehumidifying air-conditioning system and method of operating the same

ABSTRACT

The quantity of heat for cooling processing air as a low temperature heat source for regenerating a desiccant to be dehumidified, by a sensible heat exchanger before reaching a low temperature heat source heat exchanger is suppressed for thereby maintaining a heat load on the low temperature heat source beat exchanger and making it possible to handle an air-conditioning load with a small sensible heat factor, A dehumidifying air-conditioning system has a path (A) for processing air to be cooled by a low temperature heat source ( 115 ) of a heat pump ( 200 ) after moisture is adsorbed therefrom by a desiccant ( 103 ), a path (B) for regenerating air which, after being heated by a high temperature heat source ( 120 ) of the heat pump, passes through the desiccant that has adsorbed moisture to regenerate the desiccant, and a path (C) for cooling air for cooling the processing air by exchanging heat with the processing air from which moisture is adsorbed by the desiccant, the arrangement being such that the processing air and the regenerating air alternately flow through the desiccant. The dehumidifying air-conditioning system has means ( 400 ) for adjusting the flow rate of the cooling air which passes through a heat exchanger ( 300 ) for cooling the processing air to variably exchange heat between the processing air and the cooling air.

TECHNICAL FIELD

The present invention relates to an air-conditioning system whichemploys a desiccant, and more particularly to an air-conditioning systemwhich employs a heat pump as a heat source for heating regenerating airand cooling processing air.

BACKGROUND ART

FIG. 7 of the accompanying drawings shows an air-conditioning systemcomprising a combination of an absorption heat pump (200: represented byHP) as a heat source and an air-conditioning unit employing a desiccant,i.e., a so-called desiccant air-conditioning unit.

The air-conditioning system comprises an air-conditioning unit having apath A for processing air from which moisture has been adsorbed by adesiccant wheel 103, a path B for regenerating air which is heated by aheat source and thereafter passes through the desiccant wheel 103 thathas adsorbed the moisture to desorb the moisture from the desiccant, andan air-conditioning unit having a sensible heat exchanger 104 betweenthe processing air from which moisture has been adsorbed and theregenerating air to be regenerated by the desiccant wheel 103 and heatedby the heat source,and an absorption heat pump 200. The regenerating airof the air-conditioning unit is heated by a heater 120 using the hightemperature heat source of the absorption heat pump 200 as a heatingsource, for thereby regenerating the desiccant, and the processing airof the air-conditioning unit is cooled by a cooler 115 using the lowtemperature heat source of the absorption heat pump as a cooling heatsource.

The air-conditioning system is arranged such that the absorption heatpump simultaneously cools the processing air and heats the regeneratingair of the desiccant air-conditioning unit. Based on drive heat appliedto the absorption heat pump from an external source, the absorption heatpump produces an effect of cooling the processing air. The desiccant isregenerated by the sum of the heat removed from the processing air bythe operation of the heat pump and the drive heat applied to theabsorption heat pump. Therefore, the drive energy applied from theexternal source is utilized in multiple ways for a high energy-savingeffect.

In this air-conditioning system, as can be seen from an air cycle shownin the psychromretric chart shown in, FIG. 8 of the accompanyingdrawings, the cooling effect of a so-called desiccant cooling cycle,which is a cooling affect (ΔQ−Δq) obtained as a result of a quantity ofheat (ΔH) applied to the regenerating air to regenerate the desiccant,is greater as the temperature of outside air (state Q) which exchangesheat with the processing air (state L) after the moisture has beenadsorbed therefrom is lower. Therefore, as a means for increasing thecooling effect of the entire system, a system of cooling air for coolingthe processing air of the state L may be provided separately from thesystem of the processing air. In this case, the cooling air ispreviously humidified to lower its temperature and exchanged heat withthe processing air for thereby increasing the cooling effect.

An example in which the separate system of cooling air is added is shownin FIG. 9 of the accompanying drawings, and state changes of air in theexample shown in FIG. 9 are shown in the psychrometric chart shown inFIG. 10 of the accompanying drawings.

The example shown in FIG. 9 differs from the system shown in FIG. 7 inthat the regenerating air.(system B) is not used as the heat exchangemedium of the sensible heat exchanger 104 which exchanges heat with theprocessing air (system A) from which moisture has been adsorbed by thedesiccant wheel 104, but another system C of cooling air is provided,and outside air (OA) is introduced into the system C and humidified andcooled by a humidifier 165 into cooling air, which is used as the heatexchange medium of the sensible heat exchanger 104 to cool theprocessing air. With this arrangement, as shown in FIG. 10, thetemperatures of the cooling air (state D) at an inlet of the sensibleheat exchanger 104 is lowered by humidification, and the, flow rate ofthe cooling air can be increased. Therefore, the heat capacity of thecooling air is increased, and the temperature of the cooled processingair (state M) is made lower than the temperature in the system shown inFIG. 7, resulting in an increased cooling effect.

In the above air-conditioning system, however, for an air-conditioningload with a sensible heat factor, i.e., when the temperature isrelatively low and the humidity is high as in a rainy season, the amountof heating by the heat pump to regenerate the desiccant to bedehumidified and the amount of cooling for processing the sensible heatof air are placed out of balance. If priority is given todehumidification, then the amount of cooling by the low temperature heatsource 115 of the heat pump becomes excessive, and the temperature ofair supplied from the air-conditioning unit is lowered to excessivelycool the air-conditioned space.

The present invention has been made in view of the above drawbacks. Itis an object of the present invention to suppress the quantity of heatfor cooling processing air as a low temperature heat source forregenerating a desiccant to be dehumidified, by a sensible heatexchanger before reaching a low temperature heat source heat exchanger,for thereby maintaining a heat load on the low temperature heat sourceheat exchanger and making it possible to handle an air-conditioning loadwith a small sensible heat factor.

DISCLOSURE OF INVENTION

According to an invention described in claim 1, there is provided adehumidifying air-conditioning system having a path for processing airto be cooled by a low temperature heat source of a heat pump aftermoisture is adsorbed therefrom by a desiccant, a path for regeneratingair which, after being heated by a high temperature heat source of theheat pump, passes through the desiccant that has adsorbed moisture toregenerate the desiccant, and a path for cooling air for cooling theprocessing air by exchanging heat with the processing air from whichmoisture is adsorbed by the desiccant, the arrangement being such thatthe processing air and the regenerating air alternately flow through thedesiccant, characterized by means for adjusting the flow rate of thecooling air which passes through a heat exchanger for cooling theprocessing air to variably exchange heat between the processing air andthe cooling air.

By adjusting the quantity of heat exchanged between the processing airand the cooling air, the dehumidifying air-conditioning system canflexibly dehumidify and cool air-conditioning loads with varioussensible heat factors, and do not excessively cool an air-conditionedspace in the dehumidifying operation.

According to an invention described in claim 2, there is provided amethod of operating the dehumidifying air-conditioning system accordingto claim 1, characterized in that the dry-bulb temperature and thehumidity of an air-conditioned space are detected, and if the detecteddry-bulb temperature is lower than a preset value and the detectedhumidity is higher than a preset value, the flow of the cooling air isstopped.

If the detected dry-bulb temperature is lower than the preset value andthe detected humidity is higher than the preset value, i.e., if it isdetected when a so-called dehumidifying operation is required, the heatexchange between the processing air and the cooling air is stopped tokeep a sensible heat load in a low temperature heat source heatexchanger of the heat pump, anti an air-conditioned space is preventedfrom being excessively cooled in the dehumidifying operation.

According to an invention described in claim 3, there is provided adehumidifying air-conditioning system having a path for processing airto be cooled by a low temperature heat source of a heat pump aftermoisture is adsorbed therefrom by a desiccant, a path for regeneratingair which, after being heated by a high temperature heat source of theheat pump, passes through the desiccant that has adsorbed moisture toregenerate the desiccant, and a path for cooling air for cooling theprocessing air by exchanging heat with the processing air from whichmoisture is adsorbed by the desiccant, the arrangement being such thatthe processing air and the regenerating air alternately flow through thedesiccant, characterized in that a flow path zone for the processing airand the regenerating air which pass through the desiccant is dividedinto at least a first zone for adsorbing moisture from the processingair and a second zone for regenerating the desiccant with theregenerating air, the first and second zones being arranged such thatthe desiccant goes through the first zone and the second zone, andreturns to the first zone, said heat pump being arranged for a lowtemperature heat source heat exchanger to exchange heat with theprocessing air and for a high temperature heat source heat exchanger toexchange heat with the regenerating air, the path for processing airbeing arranged to extend from an inlet for the processing air via saidfirst zone, a first sensible heat exchanger, said low temperature heatsource heat exchanger, and a first humidifier, to an outlet for theprocessing air, the path for regenerating air being arranged to extendfrom an inlet for the regenerating air via a second sensible heatexchanger, said high temperature heat source heat exchanger, said secondzone, and the second sensible heat exchanger, to an outlet for theregenerating air, the path for cooling air being arranged to extend froman inlet for the cooling air via a second humidifier and the firstsensible heat exchanger to an outlet for the cooling air, thearrangement being such that the processing air and the cooling air arein heat exchanging relationship to each other in the first sensible heatexchanger, and the regenerating air and the regenerating air are in heatexchanging relationship to each other in the second sensible heatexchanger, and the flow rate of said cooling air is adjusted to variablyexchange heat between the processing air and the cooling air.

By thus adjusting the quantity of heat exchanged between the processingair and the cooling air, the dehumidifying air-conditioning system canflexibly dehumidify and cool air-conditioning loads with varioussensible heat factors. In the dehumidifying operation, by suppressingthe quantity of heat for cooling the processing air as the lowtemperature heat source for regenerating the desiccant by the firstsensible heat exchanger before reaching the low temperature beat sourceheat exchanger, it, is possible to maintain a heat load on the lowtemperature heat source heat exchanger, and the air-conditioned space isprevented from being excessively cooled in the dehumidifying operation.It the sensible heat load for air-conditioning is large, a heat exchangeis carried out by the first. sensible heat exchanger to lower the outlettemperature of the processing air in the heat pump, so that a coolingoperation can be also performed.

According to an invention described in claim 4, the dehumidifyingair-conditioning system according to claim 3 is characterized in thatthe desiccant is in the shape of a wheel, and rotates to go through thefirst zone and the second zone, and return to the first zone.

Since the desiccant is in the shape of a wheel and rotated, the processof adsorbing moisture with the desiccant and the process of regeneratingthe desiccant with the heat pump can successively be carried out.

According to an invention described in claim 5, there is provided amethod of operating the dehumidifying air-conditions system according toclaim 3 or 4 is characterized in that the heat pump comprises a vaporcompression heat pump having a compressor, the dry-bulb temperature andhumidity of air in an air-conditioned space are detected; if thedry-bulb temperature is higher than a preset value and the humidity ishigher than a preset value, then in a first mode of operation, thecooling air is exchanged heat with the processing air, the firsthumidifier is inactivated, and the compressor is operated with a growingcapability as the absolute value of the difference between the dry-bulbtemperature and the preset value therefor increases; if the dry-bulbtemperature is higher than the preset value and the humidity is lowerthan the preset value, then in a second mode of operation, the coolingair is exchanged heat with the processing air, the first humidifier isoperated, and the compressor is operated with a growing capability asthe absolute value of the difference between the dry-bulb temperatureand the preset value therefor increases; if the dry-bulb temperature islower than the preset value and the humidity is lower than the presetvalue, then in a third mode of operation, the cooling air is caused toexchange heat with the processing air while the flow rate of the coolingair is reduced as the absolute value of the difference between thedry-bulb temperature and the preset value therefor increases, the firsthumidifier is inactivated, and the compressor is operated with adecreasing capability as the absolute value of the difference betweenthe dry-bulb temperature and the preset value therefor increases; and ifthe dry-bulb temperature is lower than the preset value and thehumidity, is higher than the preset value, then in a fourth mode ofoperation, the flow of the cooling air is stopped, the first and secondhumidifiers are inactivated, and the compressor is operated with agrowing capability as the absolute value of the difference between thehumidity and the preset value therefor increases.

By thus detecting the sensible heat load and the latent heat load of theair-conditioning load and adjusting the compressor, the flow rate of thecooling air, and the humidifiers, both the dehumidifying operation andthe cooling operation can flexibly be performed depending on thesensible heat factor of the air-conditioning load;

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view showing a basic arrangement of a dehumidifyingair-conditioning system according to a first embodiment of the presentinvention;

FIG. 2 is a psychrometric chart illustrative of operation of thedehumidifying air-conditioning system, according to the first embodimentof the present invention;

FIG. 3 is a view showing a basic arrangement of a dehumidifyingair-conditioning system according to a second embodiment of the presentinvention;

FIG. 4 is a psychrometric chart illustrative of a first mode ofoperation of the dehumidifying air-conditioning system according to thesecond embodiment of the present invention;

FIG. 5 is a psychrometric chart illustrative of a second mode ofoperation of the dehumidifying air-conditioning system according to thesecond embodiment of the present invention;

FIG. 6 is a psychrometric chart illustrative of a third mode ofoperation of the dehumidifying air-conditioning system according to thesecond embodiment of the present invention;

FIG. 7 is a view showing an air-conditioning system comprising acombination of an absorption heat pump and a conventional desiccantair-conditioning unit;

FIG. 8 is a psychrometric chart illustrative of operation of theair-conditioning system shown in FIG. 7;

FIG. 9 is a view showing an air-conditioning system which has a separatesystem of cooling air; and

FIG. 10 is a psychrometric chart illustrative of operation of theair-conditioning system shown in FIG. 9.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of dehumidifying air-conditioning systems according to thepresent invention will be described below with reference to thedrawings.

FIG. 1 is a view showing a basic arrangement of a dehumidifyingair-conditioning system according to a first embodiment of the presentinvention.

In this embodiment, a heat pump 200 comprises a vapor compression heatpump. The vapor compression heat pump comprises a compressor 260, a lowtemperature heat source heat exchanger (evaporator) 115, a hightemperature heat source heat exchanger (condenser) 120, and an expansionvalve 270, forming a vapor compression refrigeration cycle. In theevaporator 115, a low-pressure refrigerant is in heat exchangingrelationship to processing air that has passed through a desiccant wheal103, and in the condenser 120, at high-pressure refrigerant is in heatexchanging relationship to regenerating air that is to pass through thedesiccant wheel 103.

The desiccant wheel 103 is arranged such that a desiccant rotates ingiven cycles across both a processing air path A and a regenerating airpath B, as in the case of the system described with reference to FIG. 9.The processing air path A connects an air-conditioned space to an inletport of a fan 102 for introducing return air via a path 107. The fan 102has an outlet port connected to a first zone of the desiccant wheel 103for performing a process of adsorbing moisture, via a path 108. Thedesiccant wheel 103 has an outlet for processing air which is connectedto a first sensible heat exchanger 300 which is in heat exchangingrelationship to cooling air, via a path 109. The sensible heat exchanger300 has an outlet for processing air which is connected to an evaporator(cooler) 115 via a path 110. The evaporator 115 has an outlet forprocessing air which is connected to a humidifier 105 via a path 111.The humidifier 105 has an outs for processing air which is connected toa processing air outlet as an air supply port via a path 112. Theprocessing air path A thus forms a cycle for processing air.

The regenerating air path B connects an inlet port of a fan 140 forintroducing outside air which will serve as regenerating air, via a path124. The fan 140 has an outlet port connected to a low-temperature fluidpassage in a second sensible heat exchanger 121 which is in heatexchanging relationship to processing air that has regenerated thedesiccant. The second sensible heat exchanger 121 has an outlet forlow-temperature regenerating air which is connected to a condenser 120via a path 126. The condenser 120 has an outlet for regenerating airwhich is connected to a second zone of the desiccant wheel 103 forperforming a process of regenerating the desiccant with regeneratingair, via a path 127. The second zone of the desiccant wheel 103 forperforming the process of regenerating the desiccant with regeneratingair has an outlet for regenerating air which is connected to ahigh-temperature fluid passage of the second sensible heat exchanger 121via a path 128. The second sensible heat exchanger 121 has ahigh-temperature fluid passage outlet connected to the external spacevia a path 129. The regenerating air path B thus forms a cycle forintroducing regenerating air from the external space and dischargingregenerating air into the external space.

A cooling air path C connects an inlet port of a fan 160 for introducingoutside air which will serve as cooling air, via a path 171. The fan 160has an outlet port connected to a heat exchanger 300 which is in heatexchanging relationship to the processing air, via a path 172. The heatexchanger assembly 300 is arranged such that the cooling air flowsupwardly in the vertical direction and the processing air flowshorizontally for a heat exchange to be carried out therebetween. Theheat exchanger 300 has an outlet for the cooling air which is connectedto the external space via a path 173, The cooling air path C thus formsa cycle for introducing cooling air from the external space anddischarging the cooling air into the external space.

Circled alphabetical letters D-V in FIG. 1 are representative ofrespective states of air which correspond to those shown in FIG. 2.

As in the case of conventional air-conditioning systems, the desiccantwhich rotates in given cycles across both the processing air path A andthe regenerating air path B is divided into the first zone which isconnected to the processing air path A via the paths 108, 109 forperforming the process of adsorbing moisture, and the second zone whichis connected to the regenerating air path B via the paths 127, 128 forperforming the process of regenerating the desiccant with theregenerating air. The desiccant goes through the first zone and thesecond zone, and returns to the first zone.

A dry-bulb temperature and humidity of an air-conditioned space 101 aredetected respectively by a temperature sensor 410 and a humidity sensor420 that are disposed in the return air path 107. The sensors 410, 420supply signals to a controller 400. If the detected dry-bulb temperatureis lower than a preset value and the detected humidity is higher than apreset value, then the controller 400 turns off the cooling air fan 160and a water supply valve 340 of the humidifier 105 to stop the flow ofthe cooling air. Otherwise, the controller 400 operates the cooling airfan 160. In this manner, the supply of the cooling air to the heatexchanger which cools the processing air is selectively turned on or offfor performing a selective heat exchange between the processing air andthe cooling air.

The vapor compression heat pump cycle of the desiccant air-conditioningsystem thus constructed will be described below. The refrigerant isevaporated in the evaporator (cooler) 115 by depriving heat of theprocessing air which has been dehumidified by the desiccant wheel 103,drawn into the compressor 260 via the path 204 and compressed thereby.The refrigerant then flows via the path 201 into the high temperatureheat source heat exchanger (condenser) 120 in which it discharges thesuper heat and condensing latent heat of the refrigerant into theregenerating air before it flows into the desiccant wheel 103.Thereafter, the refrigerant flows through the path 202 to reach theexpansion valve 270 in which it is reduced in pressure and expanded, andflows back into the evaporator (cooler) 115.

Operation of the dehumidifying air-conditioning system which uses theheat pump 200 as a heat source will be described below with reference tothe psychrometric charts shown in FIGS. 2 and 10.

First, a mode of operation in which the fan 160 is turned off to stopthe flow of the cooling air if the detected dry-bulb temperature islower than a preset value and the detected humidity is higher than apreset value, will be described below.

Introduced return air (processing air: state K) is drawn via the path107 by the fan 102, increased in pressure, and supplied via the path 108to the first zone of the desiccant wheel 103 where moisture in the airis adsorbed by the desiccant. In the first zone of the desiccant wheel103 the humidity, ratio of the air is lowered, and the temperature ofthe air is increased by the heat of adsorption (state L). The air whosehumidity is lowered and temperature is increased is sent via the path109 to the first sensible heat exchanger 300. Since no cooling air flowsin the first sensible heat exchanger 300, the air flows through thefirst sensible heat exchanger 300 (state M=L) and flows via the path 110into the evaporator (cooler) 115 which cools the air (state N). Thecooled processing air is delivered to the humidifier 105. Since thewater supply valve 340 is closed based on a detected low roomtemperature and a detected high room humidity, the humidifier 105 doesnot humidify the processing air (state P=N). The processing air isreturned via the path 112 as supply air to the air-conditioned space.

The desiccant wheel is regenerated as follows: outside air (state Q) tobe used as regenerating air is drawn via the path 124 by the fan 140,increased in pressure, and supplied to the sensible heat exchanger 121where the air exchanges heat with the regenerating air (state U) thathas regenerated the desiccant and is increased in temperature (state R).The regenerating air flows via the path 126 into the condenser 120 wherethe regenerating air is heated by the refrigerant and increased intemperature (state T). The regenerating air which has left the condenser220 passes through the second zone of the desiccant wheel 103 forregenerating the desiccant with the, regenerating air, removes moisturefrom the desiccant wheel 103 to regenerate the desiccant wheel 103(state U). The regenerating air (state U) which has passed through thedesiccant wheel 103 flows via the path 128 into the sensible heatexchanger 121 where it is reduced in temperature (state V) by exchangingheat with the regenerating air (state Q) prior to regenerating thedesiccant. The regenerating air is then discharged via the path 129 asdischarged air into the external space. The cooling air does not flowbecause the fan 160 is inactivated.

In the above mode of operation in which the fan 160 is turned off tostop the flow of the cooling air if the detected dry-bulb temperature islower than a preset value and the detected humidity is higher than apreset value, the state (state M) of the outlet of the first sensibleheat exchanger 300 for the processing air is represented by a hightemperature as it is not cooled by the cooling air. Hence, thetemperature of the processing air at the outlet of the evaporator 115 ofthe heat pump 200 is high. Since a heat source that can be recovered bythe low temperature heat Source of the heat pump 200 is ensured, a heatsource for regenerating the desiccant can be ensured which is dischargedby the high temperature heat source of the heat pump 200 withoutlowering the room temperature.

Next, a mode of operation in which the fan 160 is turned on to cause thecooling air to flow if the detected dry-bulb temperature is higher thanthe preset value and the detected humidity is higher than the presetvalue, will be described below, This mode of operation does not differfrom the operation shown in FIG. 10, but is carried out as follows:Introduced return air (processing airs state K) is drawn via the path107 by the fan 102, increased in pressure, and supplied via the path 108to the first zone of the desiccant wheel 103 where moisture in the airis adsorbed by the desiccant. In the first zone of the desiccant wheel103, the humidity ratio of the air is lowered, and the temperature ofthe air is increased by the heat of adsorption (state L). The air whosehumidity is lowered and temperature is increased is sent via the path109 to the first sensible heat exchanger 300 where the air is cooled bya heat exchange with the cooling air (state M). The cooled air flows viathe path 110 into the evaporator (cooler) 115 which cools the air (stateN). The cooled processing air is delivered to the humidifier 105 wherethe temperature of the air is lowered in an isenthalpic process by theway of water injection or evaporative cooling (state P), after which theair is returned via the path 112 as supply air to the air-conditionedspace.

As in the case of the foregoing mode of operation, the desiccant wheelis regenerated as follows: Outside air (state Q) to be used asregenerating air is drawn via the path 124 by the fan 140, increased inpressure, and supplied to the sensible heat exchanger 121 where the airexchanges heat with the regenerating air (state U) that has regeneratedthe desiccant and is increased in temperature (state R). Theregenerating air flows via the path 126 into the condenser 120 where theregenerating air is heated by the refrigerant and increased intemperature (state T). The regenerating air which has left the condenser220 passes through the second zone of the desiccant wheel 103 forregenerating the desiccant with the regenerating air, removes moisturefrom the desiccant wheel 103 to regenerate the desiccant wheel 103(state U). The regenerating air (state U) which has passed through thedesiccant wheel 103 flows via the path 128 into the sensible heatexchanger 121 where it is reduced in temperature (state V) by exchangingheat with the regenerating air (state Q) prior to regenerating thedesiccant. The regenerating air is then discharged via the path 129 asdischarged air into the external space.

The cooling air cools the processing air as follows: The outside air(state Q) used as the cooling air is drawn via the path 171 by the tan160, increased in pressure, and supplied to the humidifier 165 where thetemperature of the air is lowered in an isenthalpic process by the wayof water injection or evaporative cooling (state D), after which the airis delivered to the first sensible heat exchanger 300 where it isreduced in temperature by exchanging heat with the cooling air (stateE). The air then leaves the first sensible heat exchanger 300, and isdischarged via the path 173 as discharged air into the external space.

In the above mode of operation in which the fan 160 is turned on tocause the cooling air to flow if the detected dry-bulb temperature ishigher than the preset value and the detected humidity is higher thanthe preset value, i.e., in the so-called cooling operation, the state(state M) of the outlet of the first sensible heat exchanger 300 for theprocessing air is represented by a temperature lower than thetemperature in the above dehumidifying operation as it is cooled by thecooling air. Hence, the temperature of the processing air at the outletof the evaporator 115 of the heat pump 200 is low. Since thelow-temperature processing air capable of handling a sensible heat loadis produced, the ordinary so-called cooling operation which can handleboth sensible and latent heat loads can be carried out, even when not inthe dehumidifying operation.

FIG. 3 shows a basic arrangement of a dehumidifying air-conditioningsystem according to a second embodiment of the present invention.

In the second embodiment, the processing air path A and the regeneratingair path B are of the same arrangement as those of the first embodimentshown in FIG. 1, and only the cooling air path C is of an arrangement,slightly different from that of the first embodiment shown in FIG. 1.Specifically, the cooling air path C connects an inlet port of the fan160 for introducing outside air which will serve as cooling air, via thepath 171. The fan 160 has an outlet port connected via the path 172 to aplate, cross flow type heat exchanger element 310 in a heat: exchangerassembly 300 which is in heat exchanging relationship to the processingair. The heat exchanger assembly 300 is arranged such that in the platecross flows type heat exchanger element 310, the cooling air flowsupwardly in the vertical direction and the processing air flowshorizontally separately from the cooling air for a heat exchange to becarried out therebetween. Water is sprayed by a pump 330 downwardly ontoa heat transfer surface for the cooling air of the plate cross flowtypes heat exchanger element 310, wetting the heat transfer surface forthe cooling air with the water. The heat exchanger assembly 300 has anoutlet for the cooling air which is connected to the external space viathe path 173. The cooling air path C thus forms a cycle for introducingcooling air from the external space and discharging the, cooling airinto the external space.

The cooling air in the above cycle thus arranged cools the processingair as follows: The outside air (state Q) used an the cooling air isdrawn via the path 171 by the fan 160, increased in pressure, andsupplied to the heat exchanger assembly 300 where the temperature of theair is lowered in an isenthalpic process by the evaporation of thedownwardly sprayed water (state D ), after which the air exchanges heatwith the cooing air via the wet heat transfer surface of the plate crossflow type heat exchanger element 310. Since the air undergoes a changeof state along a saturation curve of a relative humidity from 95 to 100%due to the evaporation of the water on the heat transfer surface, theair is slightly increased in temperature (state A), leaves the heatexchanger assembly 300, and is discharged via the path 173 as dischargedair into the external space. In this embodiment as described above, theheat exchanger element 310 for exchanging heat between the processingair and the cooling air comprises a plate cross flow type heat exchangerelement, the cooling air flows upwardly in the vertical direction andthe processing air flows horizontally, and water is sprayed downwardlyonto the heat transfer surface for the cooling air to wet the heattransfer surface with the water with this arrangement, the heatexchanger has an increased level of performance, and can achieve thesame high level of performance as a rotary heat exchanged with a smallNTU (number of thermal unit) in spite of the cross flow type heatexchanger. However, details of the heat exchanger will not be describedbelow as it does not fall in the scope of claims of the presentinvention.

In this embodiment, a controller 400 provided as a control devicereceives signals from the dry-bulb temperature sensor 410 and thehumidity sensor 420 that are disposed in the return air path 107extending from the air-conditioned space. The controller 400 alsocontrols an inverter 460 of the fan 160 for the cooling air to regulatethe rotational speed thereof, adjusts the opening of a water supplyvalve 340 of the humidifier 105, controls an inverter 450 of therefrigerant compressor 260 to regulate the rotational speed thereof, andcontrols an inverter 440 of the fan 140 for the regenerating air toregulate the rotational speed thereof.

The dehumidifying air-conditioning system is operated in various modesof operation as shown in Table 1. Specifically, in a first mode ofoperation (dehumidifying cooling mode), the dry-bulb temperature andhumidity of air in the air-conditioned space are detected, and if thedry-bulb temperature is higher than a preset value and the humidity ishigher than a preset value, then the fan 460 for the cooling air isrotated at a rated rotational speed, and the humidifier 105 isinactivated. In this case, the water injection pump 330 of the heatexchanger assembly 300 is operated, and the compressor 260 is operatedwith a growing capability as the absolute value of the differencebetween the dry-bulb temperature and the preset value thereforincreases, with the flow rate of the regenerating air being proportionalto the capability (rotational speed) of the compressor 260.

TABLE 1 Various modes of operation and settings Mode of DehumidifyingCooling Weak De- operation cooling cooling humidifying CompressorControlled by Controlled Controlled Controlled capability dry-bulb bydry-bulb by dry-bulb by humidity setting temperature temperaturetemperature Rate of Proportional Proportional Proportional Proportionalregenerating to the to the to the to the air capability of capabilitycapability capability of compressor of of compressor compressorcompressor Rate of Rated Rated Controlled Stopped cooling air rotationalrotational by dry-bulb speed speed temperature Water Operated OperatedInactivated Inactivated injection pump 330 Humidifying Closed ControlledClosed Closed valve 340 by dry-bulb temperature Dry-bulb High High LowLow temperature sensor signal Humidity High Low Low High sensor signal

In a second mode of operation (cooling mode), if the dry-bulbtemperature is higher than the preset value and, the humidity is lowerthan the preset value, then the fan 460 for the cooling air is rotatedat the rated rotational speed, and the humidifier 105 is operated toincrease the amount of humidification as the absolute value of the,difference between the dry-bulb temperature and the preset valuetherefor increases. In this case, the water injection pump 330 of theheat exchanger 300 is operated, and the compressor 260 is operated witha growing capability as the absolute value of the difference between thedry-bulb temperature and the preset value therefor increases, with theflow rate of the regenerating air being proportional to the capability(rotational speed) of the compressor 260.

In a third mode of operation (weak cooling mode), if the dry-bulbtemperature is lower than the preset value and the humidity is lowerthan the preset value, then the fan 460 for the cooling air is rotatedat a rotational speed which decreases as the absolute value of thedifference between the dry-bulb temperature and the preset valuestherefor increases, and the humidifier 105 is inactivated. In this case,the water injection pump 330 of the heat exchanger 300 is inactivated,and the compressor 260 is operated with a growing capability, as theabsolute value of the difference between the dry-bulb temperature andthe preset value therefor increases, with the flow rate of theregenerating air being proportional to the capability (rotational speed)of the compressor 260.

In a fourth mode of operation (dehumidifying mode), if the dry-bulbtemperature is lower than the preset value and the humidity is higherthan the preset value, then the fan 460 for the cooling air isinactivated, the humidifier 105 in inactivated, and the water injectionpump, 330 of the heat exchanger 300 is inactivated. In this case, thecompressor 260 is operated with a growing capability as the absolutevalue of the difference between the dry-bulb temperature and the presetvalue therefor increases, with the flow rate of the regenerating airbeing proportional to the capability (rotational speed) of thecompressor 260.

The humidity used herein is preferably representative humidity ratio.However, the humidity sensor 320 may be a relative humidity sensor, andhumidity ratio may be calculated from a signal from such a relativehumidity sensor and a signal from the dry-bulb temperature sensor 310.Similarly, an enthalpy sensor may be used, and humidity ratio may becalculated from a signal from such an enthalpy sensor and a signal fromthe dry-bulb temperature sensor 310. The humidity sensor 320 maycomprise. a dew-point sensor equivalent to a humidity ratio sensor.

Details of the modes of operation will be described below.

The dehumidifying mode as the first mode of operation will be describedbelow, FIG. 4 shows an air cycle of this node of operation. In the cycleshown in FIG. 4, since the humidifier 105 in the processing air path isnot activated, the state (state P) of the outlet for the processing airbecomes the same as the state (state N) of the outlet of the lowtemperature heat source heat exchanger. Therefore, the humidity ratio ofthe supply air is lower and the dry-bulb temperature thereof is higherthan those in the cooling operation shown in FIG. 10. Since the dry-bulbtemperature and humidity ratio of the supply air are lower than those inthe air-conditioned space, the states in the air-conditioned spaceprogressively approach preset values, In this mode of operation, becausethe capability of the compressor 260 increases as the dry-bulbtemperature is higher, the temperature and humidity differences of thesupply air from preset values increase, resulting in an increasedability to cool and dehumidify the air-conditioned space to the presetvalues.

The cooling mode as the second mode of operation will be describedbelow. FIG. 5 shows an air cycle of this mode of operation. The cycle ofthe processing air in this mode of operation is the same as that in thecooling mode shown in FIG. 10. However, the process of exchanging heatbetween the cooling air and the processing air differs from that of thecooling mode shown in FIG. 10, and the cooling effect on the processingair is large because the process varies along a relative humidity curveranging from 95 to 100%. In this mode of operation, since adehumidifying ability (latent heat processing ability) can be convertedinto a sensible heat processing ability by the humidifier 105, thesensible heat processing ability is increased, and loads with varioussensible heat factors can be handled. Therefore, inasmuch the dry-bulbof the supply air is lower than that in the air-conditioned space, thestates in the air-conditioned space progressively approach presetvalues. In this mode of operation, because the capability of thecompressor 260 increases as the dry-bulb temperature is higher, thetemperature difference of the supply air from a preset value increases,resulting in an increased ability to cool the air-conditioned space tothe preset value.

The weak cooling mode as the third mode of operation will be describedbelow. FIG. 6 shows an air cycle of this mode of operation. As shown inFIG. 6, the water injection mechanism 330 of the heat exchanger assembly300 is inactivated, and the tan 160 for the cooling air ininverter-controlled to reduce the flow rate of the cooling air.Therefore, the quantity of heat for cooling the processing air of thestate L which exchanges heat with the cooling air is reduced to increasethe temperature of the state M. Therefore, the temperature of theprocessing air of the state N after being cooled by the low temperatureheat source of the heat pump 200 is also increased, thus reducing thesensible heat processing ability. In this mode of operation, moreover,the capability of the compressor 260 is reduced as the dry-bulbtemperature is lower, reducing the cooling capability and thedehumidifying capability of the supply air and increasing theair-conditioning load for thereby humidifying and heating theair-conditioned space to the preset values. By thus lowering the coolingcapability and the dehumidifying capability so as to be smaller than theair-conditioning load of the air-conditioned space, the states of theair-conditioned space can be shifted toward the preset values.

The dehumidifying mode as the fourth mode of operation will be describedbelow. The air cycle of this mode of operation is the same as that ofthe dehumidifying mode shown in FIG. 2 according to the firstembodiment. In the operation in which the fan 160 is turned off to stopthe flow of the cooling air if the detected dry-bulb temperature islower than the preset value and the detected humidity is higher than thepreset value, the state (state M) of the outlet of the heat exchangerassembly 300 for the processing air is represented by a high temperatureas it is not cooled by the cooling air. Hence, the temperature of theprocessing air at the outlet of the evaporator 115 of the heat pump 200is high. Since a heat source that can be recovered by the lowtemperature heat source of the heat pump 200 is ensured, a heat sourcefor regenerating the desiccant can be ensured which is discharged by thehigh temperature heat source of the heat pump 200 without lower the roomtemperature. Therefore, even it only a latent heat load is present inthe air-conditioned space, since the supply air can be set to a suitabletemperature while being lower in humidity than the air-conditionedspace, the states of the air-conditioned space can be shifted toward thepreset values. In this mode of operation, the capability of thecompressor 260 increases as the humidity is higher, and the humiditydifference of the supply air from a preset value increases, resulting inan increased ability to humidify the air-conditioned space to the presetvalue.

In the above four modes of operation, the flow rate of the regeneratingair increases and decreases in proportion of the rotational speed of thecompressor 260. Specifically, the quantity of heat applied to theregenerating air decreases as the capability of the compressor 260decreases. Therefore, if the flow rate of the regenerating air isconstant, then the regenerating air cannot be heated to a temperaturenecessary to regenerates the desiccant. In order to avoid this drawback,when the capability of the compressor 260 decreases and the quantity ofheat applied to the regenerating air decreases, the flow rate of theregenerating air is reduced to keep the regenerating temperature.Instead of varying the flow rates of the regenerating air in proportionof the rotational speed of the compressor 260, the temperature of theregenerating air outlet or the refrigerant outlet of the hightemperature heat source heat exchanger (condenser) 120 may be detectedvia the path 127 or 202, and the rotational speed of the fan 140 may becontrolled to keep the detected temperature constant.

According to the present invention, as described above, the quantity ofheat for cooling the processing air which serves as the low temperatureheat source for regenerating the desiccant to be dehumidified, by thensensible heat exchanger 104 prior to reaching the low temperature heatsource heat exchanger 115 is adjusted to keep a heat load in the lowtemperature heat source heat exchanger so as to be able to handle anair-conditioning load with a sensible heat factor.

The embodiments of the present invention use the vapor compression heatpump as the heat source. However, as disclosed by the inventors inJapanese laid-open patent publication No. 9-170639, Japanese laid-openpatent publication No. 9-170840, Japanese laid-open patent publicationNo. 9-178286, and Japanese laid-open patent publication No. 9-178287, anair-conditioning system may be arranged such that an absorption heatpump is used and connected to a high temperature heat source heatexchanger and a low temperature heat source heat exchanger by cold andhot water paths, providing the same advantages with respect to theinventions of claims 1 through 4.

According to the present invention, as described above, in adehumidifying air-conditioning system having a path for processing airto be cooled by a low temperature heat source of a heat pump aftermoisture is adsorbed therefrom by a desiccant, a path for regeneratingair which, after being heated by a high temperature heat source of theheat pump, passes through the desiccant that has adsorbed moisture toregenerate the desiccant, and a path for cooling air for cooling theprocessing air by exchanging heat with the processing air from whichmoisture is adsorbed by the desiccant, the arrangement being such thatthe processing air and the regenerating air alternately flow through thedesiccant, the flow rate of the cooling air which passes through a heatexchanger for cooling the processing air is adjusted to variablyexchange heat between the processing air and the cooling air. With thisarrangement, it is possible to carry out not only an ordinary coolingmode of operation but also a dehumidifying mode of operation to keep thetemperature of the processing air outlet high. Therefore, there are thusprovided an air-conditioning system which can achieve an excellentdehumidifying capability, can flexibly handle an air-conditioning load,and can save energy, and a method of operating such an air-conditioningsystem.

INDUSTRIAL APPLICABILITY

The present invention is preferably applicable to an air-conditioningsystem for use in general houses or larger buildings such as ofsupermarkets, offices, and others.

What is claimed is:
 1. A dehumidifying air-conditioning system having apath for processing air to be cooled by a low temperature heat source ofa heat pump after moisture is adsorbed therefrom by a desiccant, a pathfor regenerating air which, after being heated by a high temperatureheat source of the heat pump, passes through the desiccant that hasadsorbed moisture to regenerate the desiccant, and a path for coolingair for cooling the processing air by exchanging heat with theprocessing air from which moisture is adsorbed by the desiccant, thearrangement being such that the processing air and the regenerating airalternately flow through the desiccant, characterized by means foradjusting the flow rate of the cooling air which passes through a heatexchanger for cooling the processing air to variably exchange heatbetween the processing air and the cooling airs.
 2. A method ofoperating a dehumidifying air-conditioning system constructed accordingto claim 1, comprising the steps of: detecting the dry-bulb temperatureand the humidity of an air-conditioned space, and, when the detecteddry-bulb temperature is lower than a preset value and the detectedhumidity is higher than a preset value, stopping the flow of the coolingair.
 3. A dehumidifying air-conditioning system having a path forprocessing air to be cooled by a low temperature heat source of a heatpump after moisture is adsorbed therefrom by a desiccant, a path forregenerating air which, after being heated by a high temperature heatsource of the heat pump, passes through the desiccant that has adsorbedmoisture to regenerate the desiccant, and a path for cooling air forcooling the processing air by exchanging heat with the processing airfrom which moisture is adsorbed by the desiccant, the arrangement beingsuch that the processing air and the regenerating air alternately flowthrough the desiccant, characterized in that a flow path zone for theprocessing air and the regenerating air which pass through the desiccantis divided into at least a first zone for adsorbing moisture from theprocessing air and a second zone for regenerating the desiccant with theregenerating air, the first and second zones being arranged such thatthe desiccant goes through the first zone and the second zone, andreturns to the first zone, said heat pump being arranged for a lowtemperature heat source heat exchanger to exchange heat with theprocessing air and for a high temperature heat source heat exchanger toexchange heat with the regenerating air, the path for processing airbeing arranged to extend from an inlet for the processing air via saidfirst zone, a first sensible heat exchanger, said low temperature healsource heat exchanger, and a first humidifier, to an outlet for theprocessing air, the path for regenerating air being arranged to extendfrom an inlet for the regenerating air via a second sensible heatexchanger, said high temperature heat source heat exchanger, said secondzone, and the second sensible heat exchanger, to an outlet for theregenerating air, the path for cooling air being arranged to extend froman inlet for the cooling air via a second humidifier and the firstsensible heat exchanger to an outlet for the cooling air, thearrangement being such that the processing air and the cooling air arein heat exchanging relationship to each other in the first sensible heatexchanger, and the regenerating air and the regenerating air are in heatexchanging relationship to each other in the second sensible heatexchanger, and the flow rate of said cooling air is adjusted to variablyexchange heat between the processing air and the cooling air.
 4. Adehumidifying air-conditioning system according to claim 3,characterized in that the desiccant is in the shape of a wheel, androtates to go through the first zone and the second zone, and return tothe first zone.
 5. A method of operating in an air-conditioned space, adehumidifying air conditioning system having a structure as recited ineither one of claim 3 or claim 4 and wherein the heat pump comprises avapor compression heat pump having a compressor, said method comprisingthe steps of: detecting a dry-bulb temperature and a humidity of air insaid air-conditioned space; when the dry-bulb temperature is higher thana preset value and the humidity is higher than a preset value, operatingsaid system in a first mode of operation in which the heat of thecooling air is exchanged with the processing air, the first humidifieris inactivated, and the compressor is operated with a growing capabilityas the absolute value of the difference between the dry-bulb temperatureand the preset value therefor increases; when the dry-bulb temperatureis higher than the preset value and the humidity is lower than thepreset value, operating said system in a second mode of operation inwhich the heat of the cooling air is exchanged with the processing air,the first humidifier is operated, and the compressor is operated with agrowing capability as the absolute value of the difference between thedry-bulb temperature and the preset value therefor increases; when thedry-bulb temperature is lower than the preset value and the humidity islower than the preset value, operating the system in a third mode ofoperation in which the cooling air is caused to exchange heat with theprocessing air while the flow rate of the cooling air is reduced as theabsolute value of the difference between the dry-bulb temperature andthe preset value therefor increases, the first humidifier isinactivated, and the compressor is operated with a decreasing capabilityas the absolute value of the difference between the dry-bulb temperatureand the preset value therefor increases; and when the dry-bulbtemperature is lower than the preset value and the humidity is higherthan the preset value, operating the system in a fourth mode ofoperation in which the flow of the cooling air is stopped, the first andsecond humidifiers are inactivated, and the compressor is operated witha growing capability as the absolute value of the difference between thehumidity and the preset value therefor increases.